Duplex telegraph



(No Model.)

G S MOTT 'Duplex Telegraph.

180.243.288.v Patented Junel 21, 1881.

( -LINE LINE FIQLE.

Invia/Tok.

GTA/6858..

N. PETERS Win-,1wlinunpzxphm-v waminmm. n. C.

UNITED STATES PATENT OFFICE.

GARRET S. MOTT, OF PHILADELPHIA, PENNSYLVANIA.

DUPLEX TELEGRAPH.

SPEC?IZEICA'LION forming part of Letters Patent No. 243,288, dated June21, 1881. Application led September 30, 1880. (No model.)

tery from affecting the home rela-y on the open ing or closing of thetransmitter; and the objects of my invention are to simplify and improvethe operation and construction of the system, and to insure thepresentation to the incoming current at each station of the same amountot' resistance under all circumstances, irrespective of the changes ofcircuit. These l objects I attain in the manner Iwill proceed todescribe, reference being had to the accompanying drawings, in which-Figure 1 is av diagram illustrating my improved system of duplextelegraphy, and Fig. 2 a diagram of a modified arrangement. Each ofthese diagrams illustrates the arrangementY of transmitter, batteries,resistance-coils, and

circuits at only one station, but as the same arrangement exists at theother station it has not been deemed necessary to illustrate it.

Referring to Fig. 1, T is the transmitter; B, an ordinary relay; M B,the main battery; E B, the equalizing-battery'; R h, an adjustablerheostat or resistance coil or box, and G the ground or earthconnection.

The armature of the transmitter T consists of a lever, A, pivoted at p,and having its opposite ends insulated from each other, and to each issecured a flat spring, s, (s,) on an insulated support, the free end ofthe spring, when in its normal position, (as indicated on the diagra1n,)bearing against the inner face of the hook-shaped end a (a) of thelever, while an adjacent stop, m, (m,) is adapted to bear on the springand break its contact with the end a (a) ofthe lever-armature when thelatter is attracted by the electromagnets of the transmitter. Theline-wire is connected with the stop m through the wire b and the mainbattery, and with the end a' of the armature-lever through the wire b,while the spring s is connected, through the wires d d, with the relayB, which is grounded through the wire el. The equalizing-battery E B isvconnected with the stop m through the wire e, and the spring s isconnected, through the wire f, rheosta-t R lt, and wire d', with therelay, while the end a of the armature-lever is connected with theground through the wires e and f', a ground-comme tion for the battery EB being made through the wires e2 andf. When -the transmitter T isopen-that is, when its armature is not attracted to theelectro-magnets-the incoming current from the line goes to the relaythrough the wire b', end a' ofthe armature-lever, spring s', and wires dd', and thence to the ground, 'while the main battery M B, having noconnection through the stop fm', is thrown out of circuit. At the sametime the equalizingbattery E B, having no connection through the stop m,is also out of circuit. On the other hand, when the transmitter isclosed the incoming current goes to the relay R through the battery M B,wire b, stop m', spring s', and wires d d', and thence to earth.

In order to neutralize the effect on the relay ofthe current from themain battery M B at the home station, as it ows through the relaytoearth on the closing ofthe home transmitter, the action of theequalizing-battery is brought into play. At the saine moment that theattraction of the armature A to the magnets of the transmitter bringsthe stop m' into contact with the spring s and breaks the Contactbetween the arm a' and spring s the spring s at the opposite end of thearmature-lever is brought into 'contact with the stop m, and theconnection between the spring s and arm a is broken, so that a currentfrom the battery E B flows through the wire e, stop m, spring s, wirej', rheostat R h, and wire d', and through the relay R to the ground,the circuit being completed by the current which flows through the wirese2 and f from the battery to the ground. The current which enters thecoils of the relay from the equalizing-battery E B is of oppositepolarity from that which flows in the same direction from the mainbattery M B at the home station, andthe resistanceR his so proportionedas to make both currents of equal strength, Vso that the effect of onecurrent on the relay ICO is neutralized by that of the other. Hence,owing to the fact that these two equal but opposing currents are causedto simultaneously enter the coils of the home relay in the samedirection, and to be drawn off simultaneously, the relay is not affectedin any way by the action ofthe holnetransmittcr, but responds only tocurrents sent over the line from the battery' at the distant station,and so records signals only from the transmitter at that station, themain batteries at the two stations, ot' course, having their oppositepoles to the line. Hence the incoming current from the main battery atthe distant station passes to the ground through the home relay in thesame direction and with the same polarity as the currentfrom the homerelay.

I prefer to put on the wire b a small resistance-box, i, presenting tothe incoming current a resistance equal to that which it has to overcomein passing through the main battery M B when it ows over the wire b. Asimilar resistance, r', may also be put on the wire e', for use inconnection with the battery E B.

In the i'noditication, Fig. 2, the principle of the invention and themethod of operation are the same. as described above; but theconstruction ot' the transmitter is somewhat changed, twoelectromagnets, or two sets of electromagnets,being combined with twoindependent armatures, a a', so as to cause the short-circuiting of thetwo batteries M B and E B, instead of throwing them out of circuit whenthe transmitter is opened, as in the arrangement described above. Thepivoting-point ot' the armature a is connected through the wire b withthe main battery M B, and through the wires d d with the relay, whilethe line-wire, also leading to said battery, is connected through thewire b with a stop, against which the armature a bears when thetransmitter is open. The equaliZing-batteryE B is grounded through thewire f', and connected, through the'wire f, rheostat B h, and wire d',with the relay, as bet'ore, and is also connected through one' wire, e,with the pivoting-point of the armature a, and through another Wire, e',with a stop, against which the said armature bears when the transmitteris open. When the transmitter T is open, therefore, the main battery' MB is short-circuited through the wire b', armature a', and wire I),while the battery E B is short-circuted through the wire c, armature a,and wire e. When the transmitter T is closed, however, and the shortcircuits opened, a current from the battery M B flows to earth throughthe coils of the relay, while a current of equal strength, but ot1opposite polarity, from the battery E B simultaneously enters NVitnessesthe coils of the relay in the same direction, and so neutralizes theeffect ot' the current from the main battery.

It will be observed that in both modifications the adjustable rheostator resistance-box R h is never thrown out of circuit, and no matterwhether the transmitter throws the equating-battery in or out of thatcircuit, the continuity ot' such circuit, so far as the rheostat B h isconcerned, is never interrupted, and an equal resistance is presented tothe incoming current under all circumstances. In the arrangement shownin the diagram Fig. l,t'or instance,the rheostat B h has always agroundconnection through the wiresfandf, whether the armature-lever ofthe transmitter be in the position shown, or be closed to throw thebattery E B in circuit. VHence that portion of the incoming currentwhich passes from the wire d to the wire j'always meets the same amountot' resistance under all circumstances.

I claim as my invention- 1. A sta-tion for a duplex-telegraph system' inwhich line-wire, transmitter, main battery, and ordinary relay betweensaid battery and the ground are combined with an equalizingbattery ofopposite polarity and a resistance and circuits, substantially asdescribed, whereby the opening of the home transmitter throws the mainbattery oft' the line, while the closing ot' the said transmitter throwsthe said battery on the line and grounds it through the home relay andsimultaneously throws a cnrrent from the equalZing-battery through thesame coils ot' the relay in the same direction.

2. A duplex-telegraph system in which the relay is between the mainbattery and the ground at each station, and the main batteries at thetwo stations have opposite poles to the line, whereby the main batteryat one station passes to the ground through the home relay in the samedirection and with the same polarity as the incoming battery from thedistant station.

3.',In a duplex-telegraph system, the combination of line-wire,transmitter, main and equalizing batteries, relay, rheostats i' and 1",and circuits, substantially as described, to present to the current fromthe distant station resistances equal to the internal resistance of fsaid batteries.

In' testimony whereot'I have signed my name to this specification in thepresence of two sub- `scribin g witnesses.

GARBET S. MOTT.

JAMES F. To'BIN, HARRY SMITH.

IOS

IIO

